>"I think tag aliases are fine, but in my opinion, tags should not have hierarchies."
Many years ago I've developed a proprietary database for a media related product. It was a NoSQL Entity-Attribute-Value database where Attribute was basically a tag. Tags had no hierarchy but query language allowed to specify sequence of attributes like Genre, Artist, Album, Title. When said sequence was not empty the result set would be a tree where each level would correspond to an attribute position as defined in query.
Many years ago I've developed a proprietary database for a media related product. It was a NoSQL Entity-Attribute-Value database where Attribute was basically a tag. Tags had no hierarchy but query language allowed to specify sequence of attributes like Genre, Artist, Album, Title. When said sequence was not empty the result set would be a tree where each level would correspond to an attribute position as defined in query.